1. Field of the Invention
This invention relates generally to the methods of manipulating nanotubes. More specifically, the invention relates to a method of retrieving and isolating nanotubes dispersed in solution.
2. Background of the Invention
Nanotubes are a novel class of nanostructures that exhibit significant mechanical, electrical, and thermal properties, thus having potential applications such as nanoscale probe devices, energy storage components, sensors, flame retardant materials, conductive ink, and electrical conductors in the aerospace, automotive, micro-electric, photovoltaic, and energy transmission industries. In addition, nanotubes may be constructed of a variety of different materials, including carbon, silicon, metal-oxide and other inorganic compounds. Nanotubes may be classified as multi-walled nanotubes (MWNT) and single walled nanotubes (SWNT). SWNT in particular exhibit remarkable properties, but are difficult to manipulate individually.
Specifically, after synthesis SWNT nanotubes demonstrate an affinity for forming into roped, bundled or entangled configurations. The aggregated nanotube bundles do not yield the theoretically advantageous properties expected by calculations. The technical advantage of dispersing nanotubes for use in organic and inorganic media has implications in creating material with uniform nanotube distribution acting as a structural, mechanical, conductive or thermal component of the material.
Aggregation and bundling of nanotubes represents a constraint for implementation of these structures to maximize their advantageous properties in nanoscale applications. Previous attempts to disperse nanotubes have included covalent and noncovalent functionalization, including long term ultra-centrifugation. The covalent functionalization is highly efficient, but results in significantly degraded physical and electrical properties. Ultra-centrifugation may produce intact and individually dispersed nanotubes, but due to the low yields of dispersed nanotubes it is inefficient.
Due to the difficulty in completely dispersing nanotube bundles, the differential control over the location and orientation of the individual nanotubes represent an additional hurdle to commercial applications. As such, the homogeneous incorporation of nanotubes in compositions has been restricted for use in macroscale materials. Methods utilizing high temperatures and lasers for post-deposition alignment have been academically tested but commercial-scale applications have not been realized. Additionally, these methods are impractical for fabricating polymer nanocomposites and microelectronics with nanotubes, as the techniques ablate, damage, or alter the nanotubes or the supporting substrate irreversibly
Consequently, there is a need for a physical method suitable for dispersing and retrieving nanotubes from suspensions for the placement, alignment with high precision and order on a substrate or embedded therein.